package main.practices.algorithmCourse.mockinterview;

import java.util.HashSet;
import java.util.Set;

/**
 * @Description:
 *               Write an algorithm to determine if a number is "happy".
 *
 *               A happy number is a number defined by the following
 *               process: Starting with any positive integer, replace the
 *               number by the sum of the squares of its digits, and repeat
 *               the process until the number equals 1 (where it will
 *               stay), or it loops endlessly in a cycle which does not
 *               include 1. Those numbers for which this process ends in 1
 *               are happy numbers.
 *
 *               Example:
 *
 *               Input: 19
 *               Output: true
 *               Explanation:
 *               12 + 92 = 82
 *               82 + 22 = 68
 *               62 + 82 = 100
 *               12 + 02 + 02 = 1
 * @Author: shenpeng
 * @Date: 2020-03-12
 */
public class HappyNumber {

    public boolean isHappy(int n) {
        Set<Integer> results = new HashSet<>();
        while (n > 1) {
            if (results.contains(n)) {
                return false;
            } else {
                results.add(n);
                String s = String.valueOf(n);
                n = 0;
                for (int i = 0; i < s.length(); i++) {
                    int num = Integer.parseInt(s.substring(i, i + 1));
                    n += num * num;
                }
            }
        }
        return true;
    }
}
